Abstract
The on-surface synthesis of covalently bonded materials differs from solution-phase synthesis in several respects. The transition from a three-dimensional reaction volume to quasi-two-dimensional confinement, as is the case for on-surface synthesis, has the potential to facilitate alternative reaction pathways to those available in solution. Ullmann-type reactions, where the surface plays a role in the coupling of aryl-halide functionalised species, has been shown to facilitate extended one- and two-dimensional structures. Here we employ a combination of scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and X-ray standing wave (XSW) analysis to perform a chemical and structural characterisation of the Ullmann-type coupling of two iodine functionalised species on a Ag(111) surface held under ultra-high vacuum (UHV) conditions. Our results allow characterisation of molecular conformations and adsorption geometries within an on-surface reaction and provide insight into the incorporation of metal adatoms within the intermediate structures of the reaction.
Highlights
The on-surface synthesis of covalently bonded materials differs from solution-phase synthesis in several respects
These studies are often performed on metallic substrates held under ultrahigh vacuum (UHV) conditions and are predominantly based upon Ullmann-type and Glaser-type coupling, other variants have been used, and common within these methodologies is the use of the substrate to drive on-surface bond-breaking reactions
The role of molecular conformation for surface adsorbed species has previously been observed to play a role in the progression of on-surface reactions[2,15], and an additional consideration is the precise role of the metal surface which have been observed to play a role in on-surface reactions
Summary
The on-surface synthesis of covalently bonded materials differs from solution-phase synthesis in several respects. Building upon approaches developed within solution phase synthetic chemistry, various on-surface synthesis protocols have been employed to produce extended 1D and 2D molecular structures; including nanoribbons[2], porphyrinbased polymers[3,4], and other structures[5,6,7] These studies are often performed on metallic substrates held under ultrahigh vacuum (UHV) conditions and are predominantly based upon Ullmann-type and Glaser-type coupling, other variants have been used, and common within these methodologies is the use of the substrate to drive on-surface bond-breaking reactions Accurate structural characterisation of adsorption geometry and molecular conformations is required to provide information on details of the underlying reaction mechanism
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